JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.6.4/jquery.min.js"></script>
<select id="lang-switch">
  <option value="en">English</option>
  <option value="es">Espanol</option>
  <option value="zh">普通話</option>
</select>

<h1><span lang="en">Title</span> <span lang="es">Titulo</span> <span lang="zh">職銜</span></h1>

<p lang="en">Welcome to my site!</p>
<p lang="es">¡Bienvenido a mi sitio web!</p>
<p lang="zh">歡迎來到我的網站!</p>

JavaScript

$('[lang="es"], [lang="zh"]').hide();

$('#lang-switch').change(function () {
  var lang = $(this).val();
  $('[lang]').hide();
  switch (lang) {
    case 'en': 
      $('[lang="en"]').show();
      break;
    case 'es':
      $('[lang="es"]').show();
      break;
    case 'zh':
      $('[lang="zh"]').show();
      break;
    default:
      $('[lang="en"]').show();
  }
});